This invention relates generally to an improved printed circuit board (PCB). More particularly, this invention relates to an improved PCB having "twisted lends" on the PCB to improve common mode rejection. Still more particularly, this invention relates to an improved PCB having complementary leads located respectively on the solder side and component side of the PCB to improve common mode rejection.
The use of printed circuit boards to develop complex circuits having a plurality of components is well known. Such boards are usually substantially planar with a component side and a solder side, to facilitate positioning components relative to the boards and to permit soldering of those components into the circuit to be automated. A bus problem exists with such PCBs, however, in that when a bus structure exists on a PCB for an appreciable distance, the circuit on the PCB is susceptible to cross talk and induced noise from outside interference. Highly accurate circuits are adversely affected by such spurious signals.
One solution that is conventional to inhibit such cross talk and induced noise is to provide the PCB with special shielding. However, such additional structure is costly both from a materials and a labor point of view, and adds to the weight of the circuit. While technically such shielding is satisfactory, its drawbacks generally outweigh its benefits.
Another possible solution is to design into the circuit a common mode rejection circuit which assists in removing such common mode signals and in removing induced noises electronically. However, such additional circuitry is particularly expensive and does not function completely satisfactorily.
Accordingly, it remains an objective in the PCB art to develop a way to encourage a common mode rejection by circuits on the PCB, while inhibiting inducing noise, without the use of complex and expensive additional components of the PCB.
It is known in the electronics art to twist pairs of leads to improve common mode rejection of signals on the respective pair of leads. Such twisting literally occurs physically in that the pair of leads is in fact twisted into an interlaced pattern. It is thus another overall aim of this invention to determine whether such known structure is applicable to PCBs.
These and other aims and objectives of this invention will become apparent to those of skill in this art when considered in light of the written description of the invention which follows taken with the accompanying drawings.